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ON COLOUR VISION AND COLOUR BLINDNESS. 259 
The four chief colour names (red, yellow, green, and blue) must 
be used in any test for colour blindness, and if a daylight test be 
required, the bead test of Edridge-Green is preferable. The chief 
difficulty from a practical point of view is the line at which rejection 
should take place, as there is every grade of transition between 
total colour blindness and the normal colour sense. If a large 
number of persons be examined with the Edridge-Green lantern 
about 25 per cent. show defects of colour perception. In the 
majority of cases these defects are slight, therefore it is necessary 
to know the nearest distance at which a coloured light must be 
recognised—t.e., the exact degree of colour weakness which is per- 
missible—and that the line of rejection should be fixed accordingly. It 
is obvious that any man having even a slight defect of colour perception 
is not quite as efficient as one not possessing this defect; this particu- 
larly applies to the shortening of the red end of the spectrum, which 
prevents the recognition of red light at the normal distance, particu- 
larly when obscured by fog. 
The Committee recommends that it be reappointed. 
The Ductless Glands.—Report of the Committee, consisting of 
Sir E. A. ScHArerR (Chairman), Professor SWALE VINCENT 
(Secretary), Professor A. B. Macanttum, Dr. lL. E. SHorsg, 
and Mrs. W. H. THompson. (Drawn up by the Secretary.) 
Tue Secretary has been continuing his investigations ‘upon various 
points connected with the physiology and the comparative anatomy 
of the ductless glands. 
A study of the distribution and the detailed histology of the accessory 
cortical adrenal bodies has been commenced, but as this involves a 
large amount of serial section cutting, the work has not progressed 
very far, and there are no new facts to report at this stage. 
An investigation into the histological changes in the thyroids and 
parathyroids (along with some of the other ductless glands) under 
varying physiological and pathological conditions (different diets, 
starvation, poisons, &c.) has been undertaken, and a large amount of 
material for examination has been collected. 
Mr. Cameron has been testing Hunter’s method of iodine estima- 
tion in organic substances. It is satisfactory for moderate amounts, 
such as are found in the sheep’s thyroid. It is not satisfactory for 
very slight traces. Comparison tests are being made with this method 
and some more recent modifications of it in the hope of finding a 
rigid test for traces of iodine (one part in 500,000). 
An initial attempt has been made to correlate other tissues with 
the thyroid as regards iodine content. No definite results have yet 
been obtained, but traces (of a second lower order of magnitude) appear 
to be present in other organs of the series of ductless glands (e.q., 
testes, ovary, adrenal, thymus). 
1 J. Biol. Chem., 1910. 
s 2 
